[Indyws6]

Greetings...
I successfully repaired a similar problem on the lid of a swimming pool filter that had to withstand much higher pressures. As mentioned in previous posts, there are no guarantees, but it's certainly worth a try. I would:

1) CAREFULLY spread the crack open enough to be sure you can completely clean it. You can pry it open using a wooden dowel or other blunt item. The idea is to give yourself room to clean the surface without damaging the internal threads.

2) Mix a small amount of 30-minute epoxy (5-minute would be just as strong but provides less time for positioning and clamping). You can get the epoxy at "home" stores...

3) Use the epoxy sparingly, but be certain to cover both sides of the face of the crack. A toothpick might be useful for getting the epoxy into the narrow end of the crack.

4) Remove whatever you were using to spread the crack open, wrap the outside with a few layers of paper towel and then clamp it until the epoxy completely sets. I would use two hose clamps side-by-side to spread the load out evenly. Be careful not to overtighten the clamps but make sure they are good and snug. Wipe any excess epoxy from the inside of the threaded area using paper towels and isopropyl alcohol.

Although the epoxy will cure in 30 minutes, I would wait at least two hours before trying to reassemble and use the pump. Remove the paper towels but re-clamp the housing before tightening a new pipe thread fitting in place. The crack will always be a weak point and the clamps will help prevent it from cracking again in the same place. Use a generous (but reasonable) amount of teflon tape and tighten the fitting only as much as needed to prevent leaks.

Good luck - I hope this helps...